Insects

What to watch for with Asian longhorned ticks and Theileria in Ohio in 2024

– Tim McDermott DVM, OSU Extension Educator, Franklin County (originally published in Farm and Dairy)

Visit go.osu.edu/BITE, your guide to ticks, mosquitoes, and other biting pests. Photo: Anna Pasternak, UK entomology graduate student

One of the worrisome things about ticks in Ohio has been the increasing numbers of ticks of medical importance to humans, companion animals, and livestock as we have gone from one tick of medical importance twenty years ago to five now, including two new ticks in the past few years. While ticks have always been a problem in cattle, the invasive Asian longhorned (ALHT) tick that was first discovered in Ohio in 2020 has demonstrated the ability to not only vector, or transmit disease to cattle, but to cause mortality in cattle through high numbers of ticks feeding upon the animals. I first wrote about ALHT  in All About Grazing in July of 2020 with the article “The Threat of Asian longhorned tick continues” and then followed up with a March 2nd, 2023 article “Managing Asian longhorned ticks on pasture” so I want to provide an update on where we are in the state of Ohio with ALHT right now.

 

 

 

 

Continue reading What to watch for with Asian longhorned ticks and Theileria in Ohio in 2024 →

Field Observations Thru September 8

Corn

Growth & Development

Most of the corn that I have seen this week is in either the R4 (Dough) or the R5 growth stage.

R5 – Dent

  • The second to last stage of corn development.
  • R5 (dent) occurs approximately 31‐33 days after silking.
  • Kernels are dented in at the top with the “milk line” separating the liquid and
    solid (starch) portions.
  • Within R5, kernels are often staged according to the progression of the milk line; i.e. ¼, ½, and ¾.
  • At the beginning of R5, kernels have 60% moisture content.
  • Stresses will reduce kernel weight at this time.

Scouting

I have heard a wide range for projected corn yields this year.  The Yield Component Method is the most widely used procedure for estimating corn yield.  While  you are out checking potential corn yields, also keep an eye out for:

  • Ear rots.
  • Stalk rots.
  • Anthracnose top dieback.
  • Stalk lodging.
  • Abnormal ear fill which identifies periods of stress.
  • Weed escapes (especially palmer & waterhemp).

Soybeans

Growth & Development

Soybeans are continuing to mature.  Last week I highlighted the R6 growth stage  the next stage is R7 the last growth stage prior to maturity.

R7 – Begining Maturity

  • One mature-colored pod anywhere on the main stem.
  • Yellow pods are moving toward maturity.
  • Tan, brown or tawny pods (depending on variety) signal physiological maturity.
  • Seeds at the R7 growth stage are at approximately 60% moisture.

Scouting

  • Foliar diseases – Sudden Death Syndrome, White Mold, and Frogeye Leaf Spot.
  • Insect feeding – Grasshoppers.
  • Weed escapes (especially Palmer and Waterhemp).

Estimating soybean yields

It is much more difficult to accurately predict soybean yield.  The process to estimate soybean yields can be found here.

County Rainfall Update

Field Observations Thru September 1

They are here!  Palmer Amaranth and Waterhemp are prevalent in MANY Knox County fields.  One female plant can produce 1,000,000 seeds.  If you find Palmer Amaranth or Waterhemp you should do whatever you can to prevent these devastating weeds from going to seed, including removing the entire plant from the field.

Continue to remain vigilant!  

Click here for tips on identifying pigweed, palmer and waterhemp.

Corn

Growth & Development

Most of the corn that I have seen this week is in either the R3 (Milk) or the R4 (Dough) growth stage.  Some of our early maturing hybrids have reached the R5 dent stage.

Scouting

Disease pressure throughout the county continues to be very low. Continue to scout for:

  • Foliar diseases – Gray Leafspot, Tar Spot, Northern Corn Leaf Blight.
  • Weed escapes (especially Palmer and Waterhemp).

Soybeans

Growth & Development

Most of the corn that I have seen this week is in the R6 (Full Seed) growth stage.  Some of the early maturity beans are entering the R7 (Beginning Maturity) stage soon.

Scouting

Disease pressure throughout the county continues to be very low.  As you continue to scout your bean fields, look for:

  • Foliar diseases – Sudden Death Syndrome, White Mold, and Frogeye Leaf Spot.
  • Insect feeding – Grasshoppers.
  • Weed escapes (especially Palmer and Waterhemp).

County Rainfall Update

Field Observations Thru August 4

Corn

Corn development continues to vary throughout the county.  After tasseling the next growth stage is R1 – Silking.

R1 – Silking.

  • At least 50% of plants in the field will have 1 or more silks emerged. Look at  only the uppermost ear on the corn plant.
  • Pollen grains will land on silks and if receptive,  fertilization will occur.
  • Silks are viable and receptive to pollen for at least 5 days.
  • The plant  uses the most water per day (0.35 inches) during R1, making it very sensitive to stresses.
    • The largest yield reduction occurs with stress at silking
  • Silks have highest water content among all parts of the corn plant.
  • Drought causes silk  elongation to slow down and pollen shed to speed up.
  • Potential kernel number is determined.
  • Maximum plant height is achieved.
  • Potassium uptake is essentially complete and nitrogen and phosphorus uptake is rapid in the plant.
  • Nutrient content by leaf analysis is highly related to the final grain yield at this time.

See all information on all corn reproductive growth stages here.

Soybeans

R3 Beginning Pod

      • A plant can have all of the following:

developing pods,    withering flowers, new open flowers and flower buds

  • Potassium uptake rates peak shortly
    after R2, ranging between 3.5-5.2 lb K2O /acre/day
  • Last growth stage to treat for white mold
  • Scout for insects and diseases.  Spray foliar insecticide or fungicide, if needed.
  • Identify water stress,
    which affects pod formation.

County Rainfall Update

 

 

 

 

 

 

 

Corn Water Requirements

Soybean Water Requirements

 

Pest of the week – Soybean Aphids

Soybean Aphids

The soybean aphid, a native of Asia, has been in the Midwest since 2000 and has quickly become a serious pest of soybeans in parts of the Midwest.

 

Identification: 

Nymph: Nymphs look similar to wingless adult aphids but are smaller. White flakes may be present near aphids; these are cast skins from nymphs molting.

Adults: The soybean aphid is a small, yellow to green aphid with distinct black tailpipes, or cornicles, on the abdomen.

Lifecycle:

As with many aphids, the soybean aphid has a complicated life cycle, that requires the presence of its overwintering host, buckthorn. One important feature of the lifecycle is the ability of female soybean aphid to reproduce live, female offspring (clones) parthenogenically during the summer months. This means that soybean aphid numbers can often increase rapidly when conditions are favorable in a soybean field. Soybean aphid are usually found in soybeans from late May through August.

Sampling: Sample 20 plants from different locations throughout the field and count the number of aphids per plant.

Economic Threshold: The economic threshold for soybean aphid is 250 soybean aphids per plant, with an increasing population density. Thus, at least two samples are needed to determine whether the population size is rising. After the R5 growth stage there is no economic return to treating.

Management Options: There are several predators, including lady beetles, which may help take care of this aphid. If populations reach 250 aphids per plant and the density is rising, then the use of an insecticide might be needed. Resistant soybean varieties are now available that offer partial control of soybean aphid, although those fields should still be scouted. For more information, visit aginsects.osu.edu and extension.psu.edu/publications/agrs-026.

Impact in Knox County: Soybean aphids have rarely reached economic threshold levels in Knox County.  Could this be the year??  Click here to see the most recent information from OSU Entomologists Kelley Tilmon and Andy Michel.

Field Observations Thru July 14

Alfalfa

2nd cutting is well underway.  Potato leafhoppers are very active. If you haven’t cut yet, continue to monitor, where damage is increasing, cut as soon as weather permits.

Click here for alfalfa insect scouting calendar

Click here for more information on Potato Leafhopper

Corn

Our corn growth varies greatly throughout the county. Some fields are beginning to tassel and some field are at V8.

V12 to V13 – Six weeks after the plant emerges, V12 begins. Moisture or nutrient deficiencies may reduce the potential number of seeds, as well as the ear size, seriously. These two components of yield have key development during the period from V10 to V17. The length of time for the plant to develop through these stages affects harvestable yield.

Early maturity hybrids normally progress through these stages in less time and have smaller ears than later hybrids. Higher plant populations are needed for earlier hybrids to produce grain yield similar to normal-maturity hybrids in the adapted region. Cultivation of plants at this time will destroy some of the plant roots. Brace roots are developing from the fifth node and the first above-ground node.

V14 to V15 – Seven weeks after the plant emerges, V14 begins. The corn plant at V15 is only 12 to 15 days (around one to five V stages) away from R1 (silking). This vegetative stage is the most critical period of seed yield determination. The number of ovules that develop silks, and thus the number of kernels, is being determined. Any nutrient or moisture deficiency or injury (such as hail or insects) may seriously reduce the number of kernels that develop.

The tassel is near full size but not visible from the top of the leaf sheaths. Silks are just beginning to grow from the upper ears. Upper-ear shoot development has surpassed that of lower ear shoots. A new leaf stage can occur every one to two days.

Brace roots from the sixth leaf node are developing, and the permanent roots have continued to elongate and proliferate, eventually reaching a depth of about 5 to 8 feet and spreading several feet in all directions. In some hybrids, brace roots also will develop from the eighth and ninth leaf nodes or even higher. Some corn plants in North Dakota may only develop 16 leaves.

Critical corn growth stages

Table 5. Postemergence Herbicides in Corn – Grasses

Table 6. Postemergence Herbicides in Corn – Broadleaves

Soybeans

Soybeans are starting to look a little bit better, however, there are still a lot of “yellow” beans throughout the county.  Two possible reasons are Yellow Flash and Soybean Cyst Nematode.  Other possibilities are seedling diseases and water-logged roots, more information on these topics next week.

After planting, the second biggest challenge we face is timely weed control.  If you haven’t already made a postemergence application, it might be time to check your fields.  Most beans (and weeds) are at stage that might warrant an application.  The links below will contain OSU Herbicide rating for postemergence applications.

Soybean Postemergence Weed Control – Grasses

Soybean Postemergence Weed Control – Broadleaves

Soybean Growth & Development – R1: Beginning Bloom

 

  • Open flower at any node on the main stem
  • Flowering begins at 3rd to 6th node (V6 to V10 stage)
  • Flowering period is 3 to 4 weeks
    –Begins ~6 to 8 weeks after emergence
    – Peaks R2 to R3; ends ~R5
  • Vertical root growth rates increase rapidly
    – As much as 1.3 to 3.2 in/day

Wheat

Wheat harvest has come to an end and most of the straw is in the barn.  From what I hear, wheat yields were pretty good with little to no disease issues.

If you removed the straw, remember to account for the additional fertilizer removal when planning for fertilizer needs next year.  Read more here.

Double crop beans have been, or are being planted now.  Click here for the Double Crop Soybean Production Guidelines from Dr. Laura Lindsey.

Misc. – Something you don’t see everyday.

I can honestly say that I have never seen one of these before! Click on the picture to see the video. If you know what it is, put your answer in the comment section.  Be sure to check back next week for the answer!

… AND THE ANSWER IS – Horsehair Worm

https://entomology.ca.uky.edu/ef613

County Rainfall Update

Corn Water Requirements

Soybean Water Requirements

Field Observations Thru July 7

Alfalfa

Recent weather has delayed 2nd cutting in many fields.  Potato leafhoppers are very active.  Continue to monitor, where damage is increasing, cut as soon as weather permits.

Click here for alfalfa insect scouting calendar

Click here for more information on Potato Leafhopper

Corn

Plenty of moisture and some welcome warm weather – What a difference a week makes!

Warmer weather has slowed slug activity and the rapid corn growth is helping these plants escape (outgrow) this damage.

Our corn growth varies greatly throughout the county.  Most of the county is between V6 and V12. However, there are some fields at V12 and beyond.

V10 to V11 – The corn plant begins a steady and rapid increase in nutrient and dry-matter accumulation. The time between the appearance of new leaves is shortened, with a new leaf appearing every two to three days.  Demand for soil nutrients and water are relatively high to meet the needs of the increased growth rate. Moisture and nutrient deficiencies at this stage will influence the growth and development of the ears markedly. Fertilizer, especially phosphorus and potassium, is needed near the roots, which do not move appreciable distances in most soils. Dry soils also may make needed nutrients less available.

I have received a few questions about postemergence herbicide applications.  Click the links below for OSU Postemergence Herbicide Ratings.

Table 5. Postemergence Herbicides in Corn – Grasses

Table 6. Postemergence Herbicides in Corn – Broadleaves

Soybeans

Ok, many soybean fields just don’t look good, especially for this time of year.  While scouting your bean fields, check for seedling diseases and water-logged roots.

Warmer weather has slowed slug activity however beans are still growing slowly and may not be able to outgrow the feeding yet – Continue to monitor your bean fields for slug feeding.

Click here for slug information

Our Soybean  growth varies throughout the county.  Most of the county is between V3 and V6. However, there are some fields at and approaching R1.

V3 through V6 – The third trifoliolate (V3) stage takes place when three trifoliolates are unrolled. In case of damage to the growing point, axillary buds permit the plants to compensate for yield or final productivity.  The unrolling of six trifoliolates indicates the V6 stage. The root system continues to grow, even expanding across a 30-inch row spacing.  The V growth stages continue as long as a plant continues to produce trifoliolates. Determinate soybean plants complete most of their vegetative growth when flowering begins. Indeterminate plants produce trifoliolates until the beginning of the seed formation stage (late reproductive period).

Wheat

When, When, When will the wheat be ready??  Wheat harvest is just getting started.  A little sunshine and continued warm weather would certainly speed up the process.

Planning on planting beans after wheat? 

Click here for the Double Crop Soybean Production Guidelines from Dr. Laura Lindsey.

Click here to view herbicide restrictions prior to planting.  Table 23 from the Ohio Weed Control guide lists these restrictions.

Misc. – Something you don’t see everyday.

I can honestly say that I have never seen one of these before! Click on the picture to see the video. If you know what it is, put your answer in the comment section.  Be sure to check back next week for the answer!

County Rainfall Update

 

Pest of the week – Japanese Beetle

Japanese Beetles

Identification:

Adult: Adults are 5/16 inches long and have metallic green bodies with bronze forewings (elytra) and clubbed antennae. The forewings do not completely cover the end of the abdomen, and there are six white tufts of hair on each side of the abdomen. Males have large spikes on the front tibia while females will have spoon-like paddles.

Lifecycle:

Larvae (grubs) feed on roots of many hosts, and overwinter. Adults emerge mid-summer and feed on hundreds of hosts, including soybeans. Adults may persist into fall. Eggs laid in the soil in July-Sept.
1 generation per year

Damage:

Injury to corn: Although Japanese beetle adults can feed on the leaves of corn plants, the main concern is silk clipping. Silk clipping may interfere with pollination and lead to reduced seed set. Additionally, adults may feed on exposed kernels, but this injury is less concerning than silk clipping. Drought stress can exacerbate the effect of silk clipping by Japanese beetles. Silk clipping usually only causes reduced pollination when a majority of corn plants have silks clipped back to less than ½ inches.

Injury to soybeans: In soybeans, Japanese beetle is part of the complex of defoliating insects. Japanese beetles cause skeletonization, which is characteristic of this species because adults feed on the leaf tissue but leave all veins intact. Aggregations of Japanese beetle adults on soybean plants can cause heavy defoliation in a particular area, but beetles are usually only feeding in the upper canopy and on a few trifoliates.

Scouting:

Corn: Obtain a representative sample of silk clipping in corn by assessing silk clipping for five random plants in five locations of the field. It is especially important to scout for silk clipping during the first five days of silking.

Soybean: Scouting for Japanese beetle in soybean involves estimating percent defoliation across the entire field and throughout the entire plant canopy. Management decisions are often made for the entire complex of defoliating insects in soybean (caterpillars, beetles, grasshoppers) since it is often difficult to distinguish between types of defoliation. Use the scouting plan in Figure 2 to estimate field-wide defoliation. Remember it is important to scout the entire field because defoliation may be concentrated at field edges, and it is important to scout the entire canopy because Japanese beetle exhibits top-down feeding behavior. Make sure that defoliating pests are still present in the field before making an insecticide application by visually looking for pests or using a sweep net.

Economic Threshold:

Corn: Foliage feeding in corn is almost never economic, though economic damage from silk clipping is possible (though rare).  A foliar insecticide is warranted if three conditions are met:

  1. Three or more beetles are present per ear;
  2. Silks have been clipped to less than ½ inch; AND
  3. Pollination is less than 50% complete.

Because adults are highly mobile, remember to continue scouting until pollination is complete. Adults can continue to reinfest fields even after an insecticide application.

Soybeans: While the damage might look startling, it is very rare that this reaches economic levels from Japanese beetle.  A rescue treatment is advised when defoliation levels reach 30% in pre-bloom stages, and 20% in bloom to pod fill.  These defoliation levels apply to the plant as a whole, not just certain leaves, and can also be used for general defoliation from more than one kind of leaf-feeding insect in soybean.

Control Options: Many insecticides are labeled for Japanese beetle grubs and adults and are very effective. However, Japanese beetle adults are highly mobile and may reinfest fields even after an insecticide application.

Corn Insect Control Table

Soybean Insect Control Table

Soybean defoliation guide:

 

Field Observations Thru June 30

Alfalfa

The time for 2nd cutting is getting closer, for some fields 2nd cutting has happened.  Continue to monitor fields for potato leafhopper.

Click here for alfalfa insect scouting calendar

Click here for more information on Potato Leafhopper

Corn

Our corn growth varies greatly throughout the county.  Most of the county is between V2 and V6. However, there are some fields at V8 and beyond.

Click here for more information on the V3 – V4 growth stage

Click here for more information on the V5 – V6 growth stage

If you  haven’t scouted your fields lately, check them now for slugs.  Slugs have been very active this year, even when we had warmer temps.  I know several fields throughout the county that have been treated.

Click here for slug information

Beans

Beans just aren’t looking very good, for a variety of reasons – emergence problems, stand counts, too much water, not enough rain, SLUGS (!), poor root development, etc.  Make sure you are scouting your fields now to determine plant health.  A 4 year comparison of Ohio eFields on-farm research has shown that soybean plant populations as low as 80,000 plants per acre can produce yield equal to or greater than plant populations of 120,000 and 160,000.

Click here to see research summary.

As I mentioned above in the corn section, if you  haven’t scouted your fields lately, check them now for slugs.  Slugs have been very active this year, even when we had warmer temps.  I know several fields throughout the county that have been treated.

Click here for slug information

Wheat

Wheat maturity is delayed a bit this year.  Mother nature, growth regulator applications or fungicide applications all could play a part in this.    If you are planning on double-crop soybeans remember to pay close attention to herbicide restrictions prior to planting.  Table 23 from the Ohio Weed Control guide lists these restrictions.

County Rainfall Update